NEW YORK (Reuters Health) - People with asthma may face
increased risk from secondhand smoke exposure while riding in
the close quarters of a vehicle, according to U.S. researchers.

In a survey covering four southern states, people exposed to
secondhand smoke in vehicles were twice as likely to have asthma
compared to those who were not exposed.

The study team cannot prove the smoke exposure caused asthma
in the people interviewed, but they warn that smoke can
seriously aggravate asthma symptoms and suggest drivers and
passengers voluntarily ban smoking in their cars.

"It's problematic from a public health perspective," said
Brian King, an epidemiologist with the Centers for Disease
Control and Prevention in Atlanta and a co-author of the study.
"Secondhand smoke is a lethal cocktail of carcinogens and
toxins. You have a dangerous exposure in a very confined
environment."

Asthma is a chronic disorder of the lungs and airways that
causes them to swell, an inflammatory response that can be
fatal. In 2007, asthma was linked to more than 3,400 U.S.
deaths, according to the American Academy of Allergy, Asthma and
Immunology. About 25 million Americans have been diagnosed with
the condition.

King and his coauthor analyzed the responses from a phone
survey of 18,000 non-smoking adults living in Indiana, Kentucky,
Louisiana or Mississippi. They found that 7.4 percent reported
having asthma, and 12.4 percent said they had been exposed to
tobacco smoke in a vehicle in the past week.

The people exposed to smoke had twice the odds of also
having asthma, the researchers report in the journal Tobacco
Control.

The study establishes a link between asthma and secondhand
smoke in cars, King said, but that does not mean one causes the
other. "We don't know what came first," he said. "All we know is
that people with asthma are exposed. It's not necessarily that
the exposure is causing the asthma."

The survey also found that among the participants with
asthma, less than 10 percent of those who established smoke-free
rules in their vehicles reported having been exposed to smoke.
That compared to 57 percent of people with asthma who did not
have smoke-free rules.

Hal Strelnick, a professor of family and social medicine at
Albert Einstein College of Medicine in New York City, encourages
people with asthma to voice their concerns when in the car with
a smoker - even though it may be challenging to speak up.

"(When) someone's giving you a ride, and they light up a
cigarette, the social dynamics are difficult," Strelnick said.
"Even people who have asthma have difficulty telling a smoker to
stop smoking in the car."

Cigarette or cigar smoke in such a confined space can be
hazardous to your health and the health of those around you,
Strelnick added. If you are a smoker driving non-smokers, ask
your passengers for permission before lighting up, or
voluntarily give up smoking in your vehicle, he advised.

Smoke is known to raise the risk for other health problems,
King said. "Exposure to secondhand smoke increases the risk for
developing health issues like cardiovascular disease and lung
cancer."